The present invention relates to an analyzer, and more particularly relates to an analyzer with a function for detecting a liquid level of a liquid when a sample or a reagent is being pipetted.
When body fluid samples such as blood, urine or the like are analyzed on analysis items to be inspected using an automatic analyzer, a movable pipetting probe is used to deliver liquid from a sample cup or a reagent bottle to a reaction container. As the pipetting probe is dipped deeper into the liquid to be delivered, an amount of the liquid attached onto the outer wall of the probe is increased and accordingly the contamination becomes larger. In order to reduce the dipped depth of the pipetting probe into the liquid as much as possible, a pipetting mechanism disclosed in, for example, U.S. Pat. No. 4,970,468 or U.S. Pat. No. 4,818,492 is used.
In the pipetting mechanism disclosed in U.S. Pat. No. 4,970,468 or U.S. Pat. No. 4,818,492, a pipetting probe is electrically connected to an electric circuit for detecting changes in electrostatic capacitance. When the pipetting probe is moved downward to a sample container or a reagent container and the probe is in contact with the liquid surface, the operation of moving the probe downward is stopped and then the liquid is sucked into the probe.
According to the inventors' experience, when a pipetting probe itself is also used as a liquid level detecting electrode and particularly the humidity of the atmosphere is low, an erroneous liquid level detecting signal is often output. Such an erroneous liquid level detection is estimated to be on the basis of the fact that the sample container and/or the reagent container are made of a non-conductive material such as plastic or glass.